This invention relates to apparatus for sterilizing bottles, cans and other containers using activated oxygen (ozone) in such a manner that the ozone produced is destroyed or reduced to a non-irritating and harmless concentration in the work area surrounding the apparatus.
Beverages and similar fluids are commonly packaged in bottles, cans, or cartons for distribution to consumers. Such containers are commonly delivered empty along a conveyor line to a filling device and then proceed to equipment which affixes a cap, crown, crimp or other closing device to the container. While it is highly desirable that these containers be sterile at the time they reach the filling device, such sterility is commonly lacking. In the case of re-useable bottles which are washed between uses, most often they are washed in hot caustic solutions which cleanse and sterilize the bottles. However, the caustic solution must be rinsed from the bottles and the water used for this purpose may be of potable quality but not necessarily sterile. Accordingly, the rinse water often contains living microorganisms which can spoil the liquid in the container. Beer, milk, vegetable and fruit juices all contain nutrients capable of supporting microbial growth under such non-sterile conditions.
New bottles are also seldom subjected to effective sterilizing conditions immediately prior to filling. While glass and synthetic plastic bottles are formed from hot melts which would insure sterility at the instant they leave the mold, from that time on they are subjected to annealing and/or cooling air currents and are conveyed through possibly dusty areas to be packed into containers and shipped under conditions substantially less than sterile.
Metal cans are formed in equipment which must be lubricated with coolants notorious for their high bacteria counts. This coolant is rinsed away in a stream of water, and, while the rinse water is often sterile, it has no residual sterilizing effect on any bacteria present in the package. Paper cartons and other containers are similarly lacking in the inherent sterility one would like to count upon in the quality packaging of most beverages.
Ultraviolet radiation is known to have germicidal properties and has, accordingly, been used to sterilize various articles including bottles. (U.S. Pat. Nos. 2,194,463 and 2,384,770 show the sterilization of bottles through such a means.) Ultraviolet radiation sources which generate ultraviolet radiation wavelengths below about 330 nanometers have germicidal properties which will destroy bacteria on direct exposure to such radiation. However, the germicidal properties of such ultraviolet radiation wavelengths quickly dissipate a short distance from the ultraviolet radiation source, and thus it is necessary to bring ultraviolet lamps generating these wavelengths into immediate continuous relationship to the articles which are sterilized thereby. Since the glass out of which most bottles are made filters out most of the sterilizing ultraviolet radiation generated by the lamps, it is necessary to insert such lamps directly into the bottles involved. Where the shape of the bottles precludes bringing the ultraviolet lamps contiguous to work surfaces of the bottles to be sterilized, the sterilizing results are unsatisfactory. Also, the requirement that the ultraviolet lamps be moved into and out of the bottles makes this bottle sterilizing operation slow, cumbersome and expensive.
It is common to heat bottles to a sterilizing temperature while being filled or after they are filled and capped. The latter method is necessary in the filling of beer bottles where the filling operation cannot take place while the bottles are raised to a pasturizing temperature because of the undesired release of carbon dioxide which would take place under filling conditions. The disadvantages of these bottle heating sterilizing methods is that the sterilizing process involves excessive energy use and costly equipment.
Ozone, a gaseous alatrope of oxygen, is known as a strong oxidant and an effective sterilant. It has been commonly used to sterilize water, but is only rarely used to sterilize other materials (e.g. Russian Pat. No. 279,895 discloses the use of ozone to sterilize medical instruments). Ozone has the advantage that once it is introduced into any container, it completely fills it, so as to reach all interior surfaces, where it will destroy any contaminating microorganisms that might be present.
It is known that ozone can be generated most efficiently by ultraviolet radiation having wavelengths below about 200 nm. Thus, ultraviolet radiation sources producing wavelengths of about 180 nm produce ozone efficiently. Ultraviolet lamps which are made with a quartz envelope will pass ultraviolet energy wavelengths centered around 185 nm to a maximum degree and, therefore, are very useful in producing ozone.
While initial efforts by us to use ultraviolet radiation at these wavelengths directed over bottles in a partially enclosed space produces ozone which sterilized the inner surfaces of the bottles, these efforts were unsatisfactory because appreciable ozone escaped into the surrounding atmosphere in irritating and possibly harmful quantities.